Would someone who's on top of all the acronyms mind spelling out exactly who the document is by and the context in which it was written?
GIDS is the Gender Identity Development Service, the clinic commissioned by the NHS to cater for children and adolescents with gender identity difficulties. The contract between the NHS and GIDS includes a service specification outlining the business need for the service, objectives, context, scope of services, what the services will actually look like and how performance of the contract will be monitored.
From a quick google, it looks like this is the final version of the NHS/GIDS contract in question, which can be found on the NHS GIDS page here.
The front end of the contract (which would include the money, actual date it was signed, etc) unsurprisingly isn't included here, but the service specification states that these services run from 1 April 2016.
The document tweeted by Nicky Clark that precipitated this thread was drafted by GIRES (Gender Identity Research and Education Society), a UK charity supporting trans and GNC people, in response to an NHS public consultation on the GIDS service specification in April 2016. GIRES' documents and their reference to the consultation can be found on their website here.
It may well be that Nicky genuinely assumed she was looking at an NHS document because it says NHS in the title, although it's unfortunate that she cropped the remainder of the title in her tweet to omit the next line that said "GIRES RESPONSE", because by leaving the GIRES letterhead on the document and removing these words, it suggests that the NHS contracted with GIRES to provide services, which wasn't the case.
The only text referring to ASD in the NHS Service Specification is:
1.2.4 Autistic spectrum disorder conditions (ASD):
There seems to be a higher prevalence of autistic spectrum disorder (ASD) conditions in clinically referred, gender dysphoric adolescents than in the general adolescent population. Holt, Skagerberg & Dunsford (2014) found that 13.3% of referrals to the service in 2012 mentioned comorbid ASD (although this is likely to be an underestimate). This compares with 9.4% in the Dutch service; whereas in the Finnish service, 26% of adolescents were diagnosed to be on the autism spectrum (Kaltiala-Heino et al. 2015).
However, there are a number of studies listed in the bibliography at the end of the final GIDS service specification for anyone who wants to dig further into the underlying sources.
For anyone who's interested, these are Transgender Trend's comments on the same service specification, to provide some balance!