TaxCalc Blog

HMRC Self Assessment APIs – Experiences and Developments

As our practitioner customers will be aware, in the latter half of 2017, we released our implementation of HMRC’s new Application Programming Interfaces (or APIs). This is data that HMRC has already received from different sources which can then be fed into the tax return. This facility has proven to be extremely useful, saving our customers a great deal of time and effort.

At TaxCalc, with 8,000 firms and a user base several times that size to look after, it’s been heartening to see that, for a while at least, these APIs have worked well. This kind of digitisation has been a new foray for HMRC and the positives for customers have outweighed any initial teething problems experienced while it has bedded down.

However, with peak filing season upon us, the increased traffic experienced since the start of January has given HMRC more headaches than we expected.

In the first instance, we’ve noticed that the system has been down at times, leading to concern from customers trying to use it.

Authorisation issues

At the time of writing, the system is currently online after being down completely for a few days. However, one issue has arisen: customers who had previously successfully authenticated with the system have had their authentications revoked by HMRC. To continue using the system, customers will now need to go through the authorisation process again.

This has led to another important issue completely beyond our control. Hours prior to signing off TaxCalc’s software update in December 2017, HMRC changed the screens that are presented in TaxCalc during the authorisation process. We need to emphasise that HMRC did this without telling us. The outcome is that customers cannot complete any new authentications without applying an update.

Never fear. Our fix is here

Fortunately, we’ve already taken action to remedy the situation and have prepared an on-demand fix. Our policy is that we generally avoid public releases in January where possible, hence making the update available upon request.

If any customers would like to download this fix, please click this link to email our Support team. You will see that we have pre-populated your subject line, so we can give priority to your email and act upon it quickly. To help us find you on our system, please include your postcode.

We’ll respond when the update has been applied. When you receive your email, simply restart TaxCalc and you’ll be notified that an update is available.

Please understand that this is a situation outside of our control.

API usage limits

You may or may not be aware that HMRC imposes a usage limit for all software companies using APIs to access or authenticate data. Think of it as being like a fairground ride. When all the seats are being used, no-one else can take the ride until a seat is free. In this instance, if during peak times, you’re using TaxCalc APIs to access HMRC while the maximum set number of users are also doing so, you may not be able to successful the first time you try. The limit is reset every 60 seconds, so a failure to authenticate or obtain data one minute may be successful a minute later. Our advice is to use the APIs at either end of the working day or outside the working day, if possible. Or just keep on trying!

HMRC API survey

As you can imagine, we’ve already provided a considerable amount of feedback to HMRC on behalf of our customers. You might be interested to know that HMRC is currently running a survey on the APIs to gather feedback directly from end users. You can have your say by clicking this link.

We do of course hope that Self Assessment season has been relatively pain-free. Roll on February 1!