Invoicing tool or ERP: What do you need?

By "lean tool" we mean a scope of work here, not a specific product: importing orders, writing invoices, printing shipping labels, passing booking data to DATEV. What an individual product can do beyond that, you check in its description.

An ERP is the leading system for the whole business: inventory, purchasing, orders, documents, and payments come together in one place. In weclapp's ERP Handel (Trade) package, this includes merchandise management, planning and purchasing, warehouse management with a mobile warehouse app, serial and batch numbers, and production. On top of that come integrations for shops such as Shopware, WooCommerce, or Shopify and for marketplaces such as Amazon, eBay, or Kaufland.de.

The smallest weclapp plan, ERP Starter, costs €39 per user per month and can only be booked monthly and cannot be combined with other packages (weclapp list price, as of October 2026). It covers invoicing and accounting, but no shop import: according to the feature list, it includes payment run, dunning run, DATEV export, and e-invoicing, but no shop integration, no marketplaces, no warehouse management, and no REST API. Check the current feature overview before signing a contract. According to the app listing, the free Shopify integration requires ERP Handel.

Go through the five questions one by one and count how often you land on "ERP". Count each requirement only once, even if it fits two questions. This is our rule of thumb, not a standard and not a measured value: with zero or one question, a tool is probably enough; with two, take a closer look; from three on, a lot speaks for an ERP. The questions do not all carry the same weight. Weight them according to your business.

Warehouse. A warehouse with manageable stock can be maintained with counting and simple inventory tracking. Multiple storage locations or batch and serial numbers need a system that knows the stock per location.

Channels. Shop plus marketplace means: inventory and orders have to come together. The Handel package names Shopware, WooCommerce, and Shopify as well as Amazon, eBay, and Kaufland.de. Whether a tool connects marketplaces, you check with the respective product. Here the question is whether inventory and orders must be correct across channels.

Purchasing. Anyone who reorders goods needs minimum stock levels, order suggestions, and goods receipt. That belongs to planning and purchasing.

Team. If one person handles everything, no coordination in the system is needed. As soon as several people work on orders and stock in parallel, it matters who sees and changes what.

Processing. At weclapp, payment run, automated dunning run, and DATEV export are part of all packages, even the smallest. They therefore do not argue for a larger package. One Handel criterion is shipping with multiple carriers: weclapp connects DHL directly, for customers from Germany and with their own DHL business customer contract. For further carriers and freight forwarders you need an additional integration, such as Fulfillment 4 weclapp.

E-invoicing (E-Rechnung) is not a sixth check question, but a prerequisite on both sides. If you sell to domestic business customers, check whether your tool or ERP can create e-invoices in the XRechnung or ZUGFeRD format. Every domestic company has had to be able to receive them since January 1, 2025; according to the BMF (German Federal Ministry of Finance), an email inbox is enough for that. Companies with more than €800,000 in prior-year revenue must issue them from January 1, 2027, all others from January 1, 2028. A simple PDF is not an e-invoice; it counts as another type of invoice only until the end of the respective transition period and only if the recipient agrees to the format (BMF, questions and answers on e-invoicing, question 11). Invoices to end consumers are exempt; the BMF lists further exceptions, such as small-amount invoices up to €250 gross and services by small businesses (questions and answers on e-invoicing, as of March 2026). In weclapp, e-invoicing is included in all packages. This does not replace tax advice.

Both fictional merchants have around 600 orders per month. The example is made up and only shows the principle.

Merchant A sells through a Shopify shop. One person takes orders, writes invoices, prints labels, and sends the booking data to the tax advisor every month. There is one warehouse and no purchasing of their own. None of the five check questions points to ERP. A lean tool can be enough.

Merchant B sells through a shop, Amazon, and eBay, has two warehouses, does their own purchasing, and works with three people in parallel. Four of the five questions point to ERP; nothing is assumed for processing. Here a lot speaks for an ERP.

The order volume is the same, the answer is not.

Calculation example ERP Handel, weclapp list price, as of October 2026, annual billing, net. Assumption: Merchant A books one license, Merchant B three. This is a calculation example, not a purchase statement.

• Merchant A: 1 × €163 = €163 per month.
• Merchant B: 3 × €163 = €489 per month.

Not included are setup, optional support packages, and additional modules. What a tool costs for Merchant A depends on the pricing model of the respective tool. The calculation for four merchant profiles is in What does an ERP cost at 500 to 10,000 orders?. weclapp offers a 30-day free trial that ends automatically.

With an ERP priced per user, you pay for the heads on the team; with a per-document pricing model, you pay for volume. Many documents with a small team speak more for per-user pricing, few documents with a larger team more for per-document pricing. The scope of functionality is not the same, though. Calculate it with your own numbers.

We are a weclapp partner and support implementations. Even so, there are cases where an ERP is the worse choice.

The future is open. If you don't yet know whether a second channel or your own warehouse is coming, you don't have to plan ahead today. A later switch is possible, but needs planning. How that works is described in How do I switch ERP while the shop keeps running? Keep the commitment in mind: with annual billing (term), according to weclapp you can only cancel at the end of the term. Licenses booked monthly cost €179 per user per month for ERP Handel (weclapp list price, as of October 2026, net) and have one month's notice.