Taxumo can submit the following attachments:
Summary Alphalist of Withheld Taxes (SAWT) with 1701 / 1701A / 1701Q / 1702Q
Summary Alphalist of Sales & Purchases (SLSP) with 2550M, 2550Q
Quarterly Alphalist of Payees (QAP) with 1601EQ
Note that these alphalists are based on data you enter in Taxumo:
For SAWT, you have to enter each received Creditable Withheld Tax Form (e.g. 2307).
For SLSP, you have to enter all VAT-relevant income and expense transactions.
For QAP, it will include all issued Creditable Withheld Tax Forms created in Taxumo.
Taxumo simply does not have any way to include any WHT entry not entered in Taxumo, any WHT Form not issued/created on Taxumo, nor any income/expense not entered properly in Taxumo as VAT Relevant.
So to make sure the attachments are complete, make sure to enter those details!